Officials in South Africa and Zimbabwe have echoed allegations by Equatorial Guinea that foreign mercenaries plotted to overthrow its president.

Zimbabwe has linked the alleged plot to 64 men detained in Harare after their plane was grounded on Sunday.

Zimbabwe claimed US, British and Spanish spy agencies were helping the "mercenaries" in the plot.

Equatorial Guinea's President Teodoro Obiang Nguema also said multinational firms were involved in the conspiracy.

According to Zimbabwe's Home Affairs Minister Kembo Mohadi, the "mercenaries" were "aided by the British secret service, that is MI6... American Central Intelligence Agency and the Spanish secret service".

'Link'

The BBC's Alastair Leithead in South Africa describes the British and American links as "spurious", but adds there is growing evidence that the mystery does relate to a coup attempt gone wrong.

South African government officials said they believed the suspected mercenaries had been en route to Equatorial Guinea to help carry out a coup, and had stopped at Harare to pick up weapons.